Vianney Halter Futur Antérieur Classic Janvier Lune et Soleil (Moon and Sun) – Equation of Time and Lunar Cycle, Platinum Edition

When he founded his manufacture in Sainte-Croix in 1994, Vianney Halter baptized it La Manufacture Janvier to pay tribute to one of the most extraordinary watchmakers of all times : Antide Janvier (1751-1835).

Antide Janvier was known as the “celestial clockmaker” because he excelled in creating timepieces representing the movements of the celestial bodies . In 2007, Vianney Halter created the Classic Janvier Lune et Soleil (Moon and Sun), displaying in addition to the official time, the Equation of Time and the Lunar Cycle. This is a strictly limited series of 12 pieces, all crafted in platinum and numbered 01 P 801 to 12 P 812.

The Classic was launched in 2000 as part of Halter’s Futur Antérieur collection. It has been deriving the concept unveiled with the Antiqua while offering a simpler watch only displaying hours, minutes and seconds within a single dial. Repeating the style elements of its elder sibling, the Classic expresses by means of the form of the case, the glass porthole, the use of rivets, the lugs, and the tang buckle, all the force of the “Futur Antérieur” concept. The production ceased after only 250 pieces made the happiness of horology connoisseurs. The Classic Janvier takes up the silhouette of the Classic but the case is enlarged up to 40 mm (vs 36 mm) and widened so as to house those two “astronomical“ complications.

Astronomy et Chronometry : Equation of Time (EoT)
At the beginning of horology, clocks used to be adjusted regarding solar dials. The latter display time as a projection of the actual position of the sun in the sky. This is called Real Solar Time. The invention of mechanical clock introduced a new concept : the Mean Solar Time. As matter of fact, clocks mechanically work on the basis of a 24 hours cycle which is the mean duration of a day (averaged out over a year) – i.e. the time for the sun to come back day after day at its highest position in the sky (meridian or noon).

Therefore, the time (i.e : strictly speaking the position of the sun in the sky) indicated by the clock is the Mean Solar Time that is slightly different than the Real Solar Time. In other words, the sun is not exactly where the clock says it is ; It may be as much as 16 minutes off. But where does this difference come from ?

Two astronomical phenomena combine and the result is real duration of a day varies along the year from 23 h 59 min 40 sec to 24 h 00 min 30 sec. First phenomenon is the earth’s axis being tilted at 23°27’ relative to its orbital plane around the sun. The second phenomenon is the shape of the earth’s orbit being elliptical rather than circular.

From one day to another, there is only a few sec variation (up to 30 sec around Christmas). But these variations accumulates and the sun can be up to 16 minutes 21 seconds behind and 14 minutes 24 seconds ahead the Solar Mean Time. This time lag could have had dramatical consequences when the position of vessels was calculated from the observed position of the sun in the sky compared with the time given by a marine chronometer.

The knowledge of the Equation of Time (difference between RST and MST) was essential as one minute lag induces a longitude error of up to 27 km on the equator. So as to feature this complication, Vianney Halter adds in the round case of the Classic, a yellow gold hand bearing a symbolic representation of the sun. Once your watch is carefully set to the Mean Solar Time of your geographical reference (e.g. the Greenwich Meridian Time) and the integrated annual calendar set to the current day of the year, you can intuitively read at a glance the Real Solar Time (at your geographical reference) by means of the hour blued steel hand and the gold sun hand. If you compare this RST to the position of the sun in the sky, you can deduct how far (in longitude) you are from your geographical reference.

That is the way that used to do HM Navy officers or les officiers de la Marine du Roy since the XVIIth century. Real Solar Time and Mean Solar Time coincide only four times per year, at approximately the 16th April, 14th June, 1st September 1 and 25th December. On these days the blued steel minutes hand and the yellow gold hand will converge.

The Moon Cycle
The moon waxes and wanes within a cycle that lasts 29 days 12 hours 44 minutes and 2,8 seconds. It is quite paradoxical to consider that watchmakers have designed long time ago moon complications so accurate (29 days 12 hours 45 minutes) that it would gain only one day after 122 years, meanwhile the display of the moon-phase on the dial is so approximate !

Vianney Halter finds it more consistent to have a reasonably accurate mechanism (his looses only one day after 2 years 7 months and 20 days of operation) while allowing the moon-phase to be set (and read) with a half-day accuracy. To display day after day the exact situation of the Moon, Halter implements a very special double hand set. One hand shows the current day of the cycle while bearing a white disk which represents the moon. On a separate hand is a black disk which gradually covers and uncovers the white gold disk, thus displaying the evolution of the phases of the moon in the sky.

A special edition for a famous name
The representations of solar time and moon cycle on the Classic Moon & Sun are inspired by a famous regulator clock that Antide Janvier designed and crafted in 1788 for France’s King Louis XVI. These masterpiece is now housed in the Musée du Temps in Besançon (Eastern France).

Today, the Manufacture Janvier gathers young talented and passionate watchmakers representing 8 different nationalities (Swiss, French, Portuguese, American, German, Danish, Italian and Japanese). They contribute to the manufacturing of exceptional timekeepers bearing Vianney Halter’s signature. Halter wants this watch to be an homage paid to Janvier as well as a grateful glance to the team working with him in La Manufacture Janvier in Sainte Croix.

Construction
Although it looks quite similar to the VH Classic, the Classic Janvier definitely is a different watch : the case in bigger as well as the strap lugs, the bezel rivets and the crown.

Finally, there is no common element with its forerunner. Furthermore, its movement was specially designed so as to accommodate the complications for the Equation of Time and the Lunar Cycle as well as the “petite seconde”(small seconds) hand. Displaying the Equation of Time requires the watch to be set on the current day of the year. For this purpose there is on the back of the mechanism a ring which is hand-engraved with 365 graduations as well as the indication of months, equinoxes and solstices. Another blued steel hand travels this ring and displays the current day that can be set by means of the central special screw with a dedicated tool.The whole mechanism, including the Equation of Time special cam, can be seen through the sapphire display back and the “mysterious mass” winding rotor.
Mysterious mass winding rotor
Setting the Equation of Time requires the watch to be set on the current day of the year. For this purpose there is on the back of the mechanism a ring which is hand-engraved with 365 graduations as well as the indication of month, equinox and solstice. Another blued steel hand displays the current day that can be set by means of the central special screw with a dedicated tool. The whole mechanism, including the Equation of Time special cam, can be seen through the sapphire display back and the “mysterious mass” winding rotor.
There is only one version of the Classic Janvier, made of platinum 950 with rhodium plated metal dials. The watch is supplied with a hand-sewn alligator leather strap available in several colours. The strap has a tang buckle in white gold. As an automatic watch including complications working on long-term cycles, the Classic Janvier requires to remain wound so as to avoid it to be fully set again. Therefore, each piece is delivered with a special edition of the rotary winding box and its certificate of authenticity.

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